three.js/src/extras/core/Curve.js

/**
 * @author zz85 / http://www.lab4games.net/zz85/blog
 * Extensible curve object
 *
 * This file contains following classes:
 *
 * THREE.Curve
 * THREE.LineCurve
 * THREE.QuadraticBezierCurve
 * THREE.CubicBezierCurve
 * THREE.SplineCurve
 * THREE.ArcCurve
 *
 **/

/**************************************************************
 *	Abstract Curve base class
 **************************************************************/

THREE.Curve = function () {

};

// Virtual base class method to overwrite and implement in subclasses
//	- t [0 .. 1]

THREE.Curve.prototype.getPoint = function ( t ) {

	console.log( "Warning, getPoint() not implemented!" );
	return null;

};

// Get point at relative position in curve according to arc length
// - u [0 .. 1]

THREE.Curve.prototype.getPointAt = function ( u ) {

	var t = this.getUtoTmapping( u );
	return this.getPoint( t );

};

// Get sequence of points using getPoint( t )

THREE.Curve.prototype.getPoints = function ( divisions ) {

	if ( !divisions ) divisions = 5;

	var d, pts = [];

	for ( d = 0; d <= divisions; d ++ ) {

		pts.push( this.getPoint( d / divisions ) );

	};

	return pts;

};

// Get sequence of points using getPointAt( u )

THREE.Curve.prototype.getSpacedPoints = function ( divisions ) {

	if ( !divisions ) divisions = 5;

	var d, pts = [];

	for ( d = 0; d <= divisions; d ++ ) {

		pts.push( this.getPointAt( d / divisions ) );

	};

	return pts;

};

// Get total curve length

THREE.Curve.prototype.getLength = function () {

	var lengths = this.getLengths();
	return lengths[ lengths.length - 1 ];

};

// Get list of cumulative segment lengths

THREE.Curve.prototype.getLengths = function ( divisions ) {

	if ( !divisions ) divisions = 200;

	if ( this.cacheArcLengths && ( this.cacheArcLengths.length == divisions + 1 ) ) {

		//console.log( "cached", this.cacheArcLengths );
		return this.cacheArcLengths;

	}

	var cache = [];
	var current, last = this.getPoint( 0 );
	var p, sum = 0;

	cache.push( 0 );

	for ( p = 1; p <= divisions; p ++ ) {

		current = this.getPoint ( p / divisions );
		sum += current.distanceTo( last );
		cache.push( sum );
		last = current;

	}

	this.cacheArcLengths = cache;

	return cache; // { sums: cache, sum:sum }; Sum is in the last element.

};

// Given u ( 0 .. 1 ), get a t to find p. This gives you points which are equi distance

THREE.Curve.prototype.getUtoTmapping = function ( u, distance ) {

	var arcLengths = this.getLengths();

	var i = 0, il = arcLengths.length;

	var targetArcLength; // The targeted u distance value to get

	if ( distance ) {

		targetArcLength = distance;

	} else {

		targetArcLength = u * arcLengths[ il - 1 ];

	}

	// // TODO Should do binary search + sub division + interpolation when needed
	// time = Date.now();
	// while ( i < il ) {
	//
	// 	i++;
	//
	// 	if ( targetArcLength < arcLengths[ i ] ) break;
	//
	// }
	//
	// i--;
	// console.log('o' , i, Date.now()- time);

	time = Date.now();

	// binary search for the index with largest value smaller than target u distance

	var low = 0, high = il - 1, comparison;

	while ( low <= high ) {

		i = Math.floor( low + ( high - low ) / 2 ); // less likely to overflow, though probably not issue here, JS doesn't really have integers, all numbers are floats

	  	comparison = arcLengths[ i ] - targetArcLength;

	  	if ( comparison < 0 ) {

			low = i + 1;
			continue;

		} else if ( comparison > 0 ) {

			high = i - 1;
			continue;

		} else {

			high = i;
			break;

			// DONE

		}

	}

	i = high;

	//console.log('b' , i, low, high, Date.now()- time);

	if ( arcLengths[ i ] == targetArcLength ) {

		var t = i / ( il - 1 );
		return t;

	}

	// we could get finer grain at lengths, or use simple interpolatation between two points

	var lengthBefore = arcLengths[ i ];
    var lengthAfter = arcLengths[ i + 1 ];

    var segmentLength = lengthAfter - lengthBefore;

    // determine where we are between the 'before' and 'after' points

    var segmentFraction = ( targetArcLength - lengthBefore ) / segmentLength;

    // add that fractional amount to t

    t = ( i + segmentFraction ) / ( il -1 );

	return t;

};

// In case any sub curve does not implement its tangent / normal finding,
// we get 2 points with a small delta and find a gradient of the 2 points
// which seems to make a reasonable approximation

THREE.Curve.prototype.getNormalVector = function( t ) {

	var vec = this.getTangent( t );

	return new THREE.Vector2( -vec.y , vec.x );

};

// Returns a unit vector tangent at t

THREE.Curve.prototype.getTangent = function( t ) {

	var delta = 0.0001;
	var t1 = t - delta;
	var t2 = t + delta;

	// Capping in case of danger

	if ( t1 < 0 ) t1 = 0;
	if ( t2 > 1 ) t2 = 1;

	var pt1 = this.getPoint( t1 );
	var pt2 = this.getPoint( t2 );

	var vec = new THREE.Vector2();
	vec.sub( pt2, pt1 );
	return vec.unit();

};


/**************************************************************
 *	Line
 **************************************************************/

THREE.LineCurve = function ( v1, v2 ) {

	if ( ! ( v1 instanceof THREE.Vector2 ) ) {

		// Fall back for old constuctor signature - should be removed over time

		THREE.LineCurve.oldConstructor.apply( this, arguments );
		return;

	}

	this.v1 = v1;
	this.v2 = v2;

};

THREE.LineCurve.oldConstructor = function ( x1, y1, x2, y2 ) {

	this.constructor( new THREE.Vector2( x1, y1 ), new THREE.Vector2( x2, y2 ) );

};

THREE.LineCurve.prototype = new THREE.Curve();
THREE.LineCurve.prototype.constructor = THREE.LineCurve;

THREE.LineCurve.prototype.getPoint = function ( t ) {

	var point = new THREE.Vector2();

	point.sub( this.v2, this.v1 );
	point.multiplyScalar( t ).addSelf( this.v1 );

	return point;

	// 	var dx = this.x2 - this.x1;
	// 	var dy = this.y2 - this.y1;
	//
	// 	var tx = this.x1 + dx * t;
	// 	var ty = this.y1 + dy * t;
	//
	// 	return new THREE.Vector2( tx, ty );

};

// Line curve is linear, so we can overwrite default getPointAt

THREE.LineCurve.prototype.getPointAt = function ( u ) {

	return this.getPoint( u );

};

THREE.LineCurve.prototype.getTangent = function( t ) {

	var tangent = new THREE.Vector2();

	tangent.sub( this.v2, this.v1 );
	tangent.normalize();

	return tangent;

};

/**************************************************************
 *	Quadratic Bezier curve
 **************************************************************/


THREE.QuadraticBezierCurve = function ( v0, v1, v2 ) {

	if ( !( v1 instanceof THREE.Vector2 ) ) {

		var args = Array.prototype.slice.call( arguments );

		v0 = new THREE.Vector2( args[ 0 ], args[ 1 ] );
		v1 = new THREE.Vector2( args[ 2 ], args[ 3 ] );
		v2 = new THREE.Vector2( args[ 4 ], args[ 5 ] );

	}

	this.v0 = v0;
	this.v1 = v1;
	this.v2 = v2;

};

THREE.QuadraticBezierCurve.prototype = new THREE.Curve();
THREE.QuadraticBezierCurve.prototype.constructor = THREE.QuadraticBezierCurve;


THREE.QuadraticBezierCurve.prototype.getPoint = function ( t ) {

	var tx, ty;

	tx = THREE.Shape.Utils.b2( t, this.v0.x, this.v1.x, this.v2.x );
	ty = THREE.Shape.Utils.b2( t, this.v0.y, this.v1.y, this.v2.y );

	return new THREE.Vector2( tx, ty );

};


THREE.QuadraticBezierCurve.prototype.getTangent = function( t ) {

	// iterate sub segments
	// 	get lengths for sub segments
	// 	if segment is bezier
	//		perform subdivisions

	// var x0, y0, x1, y1, x2, y2;

	// x0 = this.actions[ 0 ].args[ 0 ];
	// y0 = this.actions[ 0 ].args[ 1 ];
	//
	// x1 = this.actions[ 1 ].args[ 0 ];
	// y1 = this.actions[ 1 ].args[ 1 ];
	//
	// x2 = this.actions[ 1 ].args[ 2 ];
	// y2 = this.actions[ 1 ].args[ 3 ];

	var tx, ty;

	tx = THREE.Curve.Utils.tangentQuadraticBezier( t, this.v0.x, this.v1.x, this.v2.x );
	ty = THREE.Curve.Utils.tangentQuadraticBezier( t, this.v0.y, this.v1.y, this.v2.y );

	// returns unit vector

	var tangent = new THREE.Vector2( tx, ty );
	tangent.normalize();

	return tangent;

};


/**************************************************************
 *	Cubic Bezier curve
 **************************************************************/

THREE.CubicBezierCurve = function ( v0, v1, v2, v3 ) {

	if ( ! ( v1 instanceof THREE.Vector2 ) ) {

		var args = Array.prototype.slice.call( arguments );

		v0 = new THREE.Vector2( args[ 0 ], args[ 1 ] );
		v1 = new THREE.Vector2( args[ 2 ], args[ 3 ] );
		v2 = new THREE.Vector2( args[ 4 ], args[ 5 ] );
		v3 = new THREE.Vector2( args[ 6 ], args[ 7 ] );

	}

	this.v0 = v0;
	this.v1 = v1;
	this.v2 = v2;
	this.v3 = v3;

};

THREE.CubicBezierCurve.prototype = new THREE.Curve();
THREE.CubicBezierCurve.prototype.constructor = THREE.CubicBezierCurve;

THREE.CubicBezierCurve.prototype.getPoint = function ( t ) {

	var tx, ty;

	tx = THREE.Shape.Utils.b3( t, this.v0.x, this.v1.x, this.v2.x, this.v3.x );
	ty = THREE.Shape.Utils.b3( t, this.v0.y, this.v1.y, this.v2.y, this.v3.y );

	return new THREE.Vector2( tx, ty );

};

THREE.CubicBezierCurve.prototype.getTangent = function( t ) {

	var tx, ty;

	tx = THREE.Curve.Utils.tangentCubicBezier( t, this.v0.x, this.v1.x, this.v2.x, this.v3.x );
	ty = THREE.Curve.Utils.tangentCubicBezier( t, this.v0.y, this.v1.y, this.v2.y, this.v3.y );

	// return normal unit vector

	var tangent = new THREE.Vector2( tx, ty );
	tangent.normalize();

	return tangent;

};


/**************************************************************
 *	Spline curve
 **************************************************************/

THREE.SplineCurve = function ( points /* array of Vector2 */ ) {

	this.points = points;

};

THREE.SplineCurve.prototype = new THREE.Curve();
THREE.SplineCurve.prototype.constructor = THREE.SplineCurve;

THREE.SplineCurve.prototype.getPoint = function ( t ) {

	var v = new THREE.Vector2();
	var c = [];
	var points = this.points, point, intPoint, weight;
	point = ( points.length - 1 ) * t;

	intPoint = Math.floor( point );
	weight = point - intPoint;

	c[ 0 ] = intPoint == 0 ? intPoint : intPoint - 1;
	c[ 1 ] = intPoint;
	c[ 2 ] = intPoint > points.length - 2 ? intPoint : intPoint + 1;
	c[ 3 ] = intPoint > points.length - 3 ? intPoint : intPoint + 2;

	v.x = THREE.Curve.Utils.interpolate( points[ c[ 0 ] ].x, points[ c[ 1 ] ].x, points[ c[ 2 ] ].x, points[ c[ 3 ] ].x, weight );
	v.y = THREE.Curve.Utils.interpolate( points[ c[ 0 ] ].y, points[ c[ 1 ] ].y, points[ c[ 2 ] ].y, points[ c[ 3 ] ].y, weight );

	return v;

};

/**************************************************************
 *	Arc curve
 **************************************************************/

THREE.ArcCurve = function ( aX, aY, aRadius,
							aStartAngle, aEndAngle,
							aClockwise ) {

	this.aX = aX;
	this.aY = aY;

	this.aRadius = aRadius;

	this.aStartAngle = aStartAngle;
	this.aEndAngle = aEndAngle;

	this.aClockwise = aClockwise;

};

THREE.ArcCurve.prototype = new THREE.Curve();
THREE.ArcCurve.prototype.constructor = THREE.ArcCurve;

THREE.ArcCurve.prototype.getPoint = function ( t ) {

	var deltaAngle = this.aEndAngle - this.aStartAngle;

	if ( !this.aClockwise ) {

		t = 1 - t;

	}

	var angle = this.aStartAngle + t * deltaAngle;

	var tx = this.aX + this.aRadius * Math.cos( angle );
	var ty = this.aY + this.aRadius * Math.sin( angle );

	return new THREE.Vector2( tx, ty );

};

/**************************************************************
 *	Utils
 **************************************************************/

THREE.Curve.Utils = {

	tangentQuadraticBezier: function ( t, p0, p1, p2 ) {

		return 2 * ( 1 - t ) * ( p1 - p0 ) + 2 * t * ( p2 - p1 );

	},

	// Puay Bing, thanks for helping with this derivative!

	tangentCubicBezier: function (t, p0, p1, p2, p3 ) {

		return -3 * p0 * (1 - t) * (1 - t)  +
			3 * p1 * (1 - t) * (1-t) - 6 *t *p1 * (1-t) +
			6 * t *  p2 * (1-t) - 3 * t * t * p2 +
			3 * t * t * p3;
	},


	tangentSpline: function ( t, p0, p1, p2, p3 ) {

		// To check if my formulas are correct

		var h00 = 6 * t * t - 6 * t; 	// derived from 2t^3 − 3t^2 + 1
		var h10 = 3 * t * t - 4 * t + 1; // t^3 − 2t^2 + t
		var h01 = -6 * t * t + 6 * t; 	// − 2t3 + 3t2
		var h11 = 3 * t * t - 2 * t;	// t3 − t2

		return h00 + h10 + h01 + h11;

	},

	// Catmull-Rom

	interpolate: function( p0, p1, p2, p3, t ) {

		var v0 = ( p2 - p0 ) * 0.5;
		var v1 = ( p3 - p1 ) * 0.5;
		var t2 = t * t;
		var t3 = t * t2;
		return ( 2 * p1 - 2 * p2 + v0 + v1 ) * t3 + ( - 3 * p1 + 3 * p2 - 2 * v0 - v1 ) * t2 + v0 * t + p1;

	}

};


/*
getPoint DONE
getLength DONE
getLengths DONE

curve.getPoints(); DONE
curve.getPointAtArcLength(t); DONE
curve.transform(params);
curve.getTangentAt(t); DONE
*/

/**************************************************************
 *	3D Curves
 **************************************************************/

// A Factory method for creating new curve subclasses

THREE.Curve.create = function( constructor, getPointFunc ) {

    var subClass = constructor;

	subClass.prototype = new THREE.Curve();

	subClass.prototype.constructor = constructor;
    subClass.prototype.getPoint = getPointFunc;

	return subClass;

};


/**************************************************************
 *	Line3D
 **************************************************************/

THREE.LineCurve3 = THREE.Curve.create(

	function ( v1, v2 ) {

		this.v1 = v1;
		this.v2 = v2;

	},

	function ( t ) {

		var r = new THREE.Vector3();


		r.sub( v2, v1 ); // diff
		r.multiplyScalar( t );
		r.addSelf( this.v1 );

		return r;

	}

);


/**************************************************************
 *	Quadratic Bezier 3D curve
 **************************************************************/

THREE.QuadraticBezierCurve3 = THREE.Curve.create(

	function ( v0, v1, v2 ) {

		this.v0 = v0;
		this.v1 = v1;
		this.v2 = v2;

	},

	function ( t ) {

		var tx, ty, tz;

		tx = THREE.Shape.Utils.b2( t, this.v0.x, this.v1.x, this.v2.x );
		ty = THREE.Shape.Utils.b2( t, this.v0.y, this.v1.y, this.v2.y );
		tz = THREE.Shape.Utils.b2( t, this.v0.z, this.v1.z, this.v2.z );

		return new THREE.Vector3( tx, ty, tz );

	}

);